Cobra CAM 88 with vintage Astatic & Precompressor

[Nagant]

Thought I'd share another recent acquisition. A Cobra CAM 88 tube type with a precompressor inline with the vintage D104. I got all three from an eBay seller Tuesday afternoon. Some scratches on the face but none on the case and the insides are excellent and clean.

Talked on it for over an hour and used it as a receiver for even longer. Everything works outstanding. Best sounding receiver of any of my radios. The precompressor has a date on the inside of August 29, 1966. It runs off of a standard 9v battery. The base the D104 is on is a bit different than other early flip switch bases I've owned in years gone by. Had to give it's flip switch two healthy doses of contact cleaner and the volume control on the radio could use a small shot of it too. Radio does about 12 PEP from a 3 watt carrier. Way it was set when received. I haven't tried tuning it and not sure I will as it's doing about what it should across all 23 channels. Everyone says it sounds really good on the air. I'm really happy with this old rig.


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[Night Crawler]

That rig looks like it's almost brand new I had an 88 that I got in 1969 and used a B&K Cobra Compressor which is similar to the one you have with a Turner 254X mike a nonpreamplified version of the Plus 2.

I have a question for you how do you like those vintage mike plugs the old Amphenol MC4M if you haven't already wait till you try to put one on

[Nagant]

Thanks Night Crawler. Sounds like only two small differences from your former setup and this one. Mine has a D104 head on the non-powered base. I don't know who made the base as it has no markings. You have any ideas on its manufacturer? The compressors are likely basically the same. I'll have to look on the inside again and see if I can find a brand name on mine. I remember there being some other writing on the inside of the precompressor besides the date.

I haven't wired many of the Amphenol mic connectors in my life time and its been many years since I last wired one. I do sort of remember them not being any fun. LOL

If you haven't seen it yet I have a post on a like new Sears 23 ch. SSB boat anchor as well.
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[Night Crawler]

. Mine has a D104 head on the non-powered base. I don't know who made the base as it has no markings. You have any ideas on its manufacturer? The compressors are likely basically the same.

That looks like a generic mike base that somebody adapted with a toggle switch to use with the D-104 stand I really wouldn't know the manufacturer.

If you could find one of these it's a tube type audio preamp compressor that would really give that 88 a nice sound I used one on a Laffayette Comstat 25A with a G-stand unamplified D-104

Demco Power Modulator
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[Nagant]

Thanks for the info. I see those Demco Power modulators every once in a while for sale on eBay. Demco items tend to bring quite a bit but I'll try to pick one up for a reasonable price sometime to try. Being they're another vintage item it appeals to me.

I took the CAM88 apart last night so I could test the tubes and give the circuitry a good check over. Everything is original and clean. No hack jobs or leaky electrolytic's. I usually do this as soon as I receive them but since this radio is so nice and it was guaranteed to be working I only gave it the shake test before I fired it up. My shake test consists of good shake once out of the box to make sure nothing is rattling. LOL Never know when it comes to tube type items that have been shipped. Since she isn't humming I didn't even bother getting my capacitor tester out. All the tubes were the original B&K branded Japan made except for the 6BQ5 and the 12AX7A. They were replacements but they tested good. The original 6BA6 was really weak and therefore I replaced it.

[airraid]

great radios i have 5 of them and also 2 of the cam 98's the black radio with chrome speaker grill. honestly i think the audio on the cobra cam 88's and 98's is better then the trams or brownings. and they do have fantastic ears. and they are great looking radios. you have a really nice one too.

[Night Crawler]

All the tubes were the original B&K branded Japan made except for the 6BQ5 and the 12AX7A.

I could see why the that's the final and audio amplifier they take the most abuse. You wouldn't happen to have the schematic for the 88 I'd like to see what makes it tick?

[PA629]

All the tubes were the original B&K branded Japan made except for the 6BQ5 and the 12AX7A.

I could see why the that's the final and audio amplifier they take the most abuse. You wouldn't happen to have the schematic for the 88 I'd like to see what makes it tick?

The 12AX7A was probably replaced due to the screen grid blowing out due to overload from the pre-amp/compressor. I have a Cam 88 that has one of the old Sentry pre-amp/compressor/clippers with the 6DS4 nuvistor triodes. It'll take the screen right out of the audio tube if you get carried away with the settings, not a big problem, just something to be aware of. The 6BQ5 is the final, probably has resistors bypassed to the screen and plate to make it run "hotter", popular idea back then for mo' powa'. I did have the complete schematic for the 88 at one time, I'll check and see if it's still around here when I get a chance, probably over the weekend. If I do find it, I'll let you know and see about arrangements to get a copy to you. Will have to be snail-mail, no technology available on this end to send it digitally.

[Night Crawler]

The 12AX7A was probably replaced due to the screen grid blowing out due to overload from the pre-amp/compressor. The 6BQ5 is the final, probably has resistors bypassed to the screen and plate to make it run "hotter", popular idea back then for mo' powa'. I did have the complete schematic for the 88 at one time, I'll check and see if it's still around here when I get a chance, probably over the weekend.

You must mean the control grid the 12AX7A is a twin triode. I remember the jumping the resistors trick I think the gain was about 1/2 watt or 1 watt at the expense of the tube.
Big deal at the time though.

I had a Ameco receive preamp that used a 6CW4 nuvistor I think the tube had the same specs as the 6DS4. It seems strange that a vhf rf amplifier tube would be used as an audio amplifier but you never know.
The nuvistor can along a little to late in an attempt to miniaturize tubes as transistors were being more fully developed at the time as a replacement.

Let me know if you come across the schematic I had an 88 back when I was around 16 that I got brand new. I remember hacking it back then when I didn't know what I was doing I'd like to look at the schematic and see exactly what I butchered

[Nagant]

I don't currently have a schematic for the 88 but I'm going to get the Sams for it. I use to have all the Sams plus extras but I sold them all some years ago when I got out of the hobby for a while. Yes I know the 6BQ5 is the final output. I wasn't sure on the 12AX7 but I suspected audio amp as I had fuzzy memory of a lot of the old 23 channel tube types using the 12AX7 for that purpose. I'll check to see if it has the mod you describe as I want it to be original. Thank you for the info on running the pre-amp to high. I have a large quantity of 12AX7's but they are fairly valuable today and therefore I don't want to be eating them up. Thus I'll run the pre-amp at low settings and see how it does. When I get the Sams I can scan the schematic and send it to you Night Crawler if PA629 is unable to find his. Again thanks for all the info on this old rig.